1. Field of the Invention
The invention relates to relates to a buckle for fastening a sport boot, especially a ski boot. The invention also relates to a boot equipped with at least one such a fastening buckle.
2. Description of Background and Other Information
The shell of a ski boot is usually fastened by bringing two flaps closer together by means of buckles. Currently available buckles include those that comprise a loop and a lever that are mounted on one flap and cooperate with a tooth or a rack mounted on the other flap. The loop is connected to the lever by means of a pin or rod. The lever is further articulated with respect to a baseplate that is fixed to the first flap and has, at its free end, a gripping portion provided to be grasped by the user's hand or fingers.
When the boot is being fastened, the end of the loop engages with a tooth of the rack, and the loop is pulled by means of the lever. In the final fastening phase, the lever is pressed flat against the shell of the boot and retains the loop by means of a knuckle-joint effect, i.e., an over-center effect. The patent documents EP 1 493 347 and EP 1 369 050 describe such fastening buckles.
The lever of a fastening buckle is subject to substantial forces, in this case the fastening force exerted on its gripping portion by the user, the resisting force opposed to the fastening by the loop of the buckle, and the force between the gripping area of the lever and the baseplate.
Moreover, the connection forces between the lever and the loop, and between the lever and the baseplate are transmitted by transverse articulation pins. And the articulation between the lever and the baseplate must also allow the connection to pass therethrough in order to enable closure of the knuckle-joint. The connection is made in two parts, each of which is cantilevered. This mode of construction requires the lever to have sufficient material thickness to guide the articulation pins, or portions of such pins.
In addition to the mechanical constraints, the designer of a fastening buckle must take into account ergonomic constraints related to the manipulation of the lever, as well as the user's positional comfort during such manipulation. The gripping zone of the lever must have a comfortable tactile sensation, and the effort required to close the buckle must be relatively measured.
Finally, boot makers increasingly impose aesthetic constraints aimed at integrating the buckle(s) into the general architecture of the boot. These constraints are expressed in terms of shapes and selection of materials, especially for the gripping zone of the lever.